Refactor Base64 encoding/decoding methods and enhance candidate not found flash message

src/Controller/QuizController.php

@@ -72,8 +72,11 @@ class QuizController extends AbstractController
         $candidate = $candidateRepository->getCandidateByHash($season, $nameHash);
 
         if (!$candidate instanceof Candidate) {
-            // Add option to add new candidate when preregister is disabled
+            if ($season->isPreregisterCandidates() === false) {
-            $this->addFlash(FlashType::Danger->value, 'Candidate not found');
+                // create candidate
+            }
+
+            $this->addFlash(FlashType::Danger->value, "Candidate {${Base64::base64_url_decode($nameHash)}} not found");
 
             return $this->redirectToRoute('enter_name', ['seasonCode' => $season->getSeasonCode()]);
         }

src/Helpers/Base64.php

@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace App\Helpers;
 
 use Safe\Exceptions\UrlException;
+use function rtrim;
 
 class Base64
 {
@@ -12,14 +13,22 @@ class Base64
     {
     }
 
-    public static function base64_url_encode(string $input): string
+    /**
+     * @param string $name name to hash
+     * @return string hashed name
+     */
+    public static function base64_url_encode(string $name): string
     {
-        return strtr(base64_encode($input), '+/', '-_');
+        return rtrim(strtr(base64_encode($name), '+/', '-_'), '=');
     }
 
-    /** @throws UrlException */
+    /**
-    public static function base64_url_decode(string $input): string
+     * @param string $hash hashed name
+     * @return string plaintext name
+     * @throws UrlException
+     */
+    public static function base64_url_decode(string $hash): string
     {
-        return \Safe\base64_decode(strtr($input, '-_', '+/'), true);
+        return \Safe\base64_decode(strtr($hash, '-_', '+/'), true);
     }
 }